41 Sustainable Coastal Infrastructure
In order to continue to have safe, secure coastlines, sustainable coastal infrastructure is essential. This can include protective coastal measures from ‘green’ to ‘gray’ as described below, but can also include things such as floating and movable pontoons, heat resistant buildings, heat tolerant roads among other things.
‘Couple Walking on Wooden Stairs’ by Mitchell Luo used under a Pexels License
Sea levels are rising at an accelerated rate as a result of global climate change.
The latest estimates indicate that values for the end-of-century (2100) range from a low of ~50 cm (~20 inches) to as high as ~310 cm (~10 feet), as a function of greenhouse gas emission scenarios and various probabilities or uncertainties, especially concerning the extent of Greenland and Antarctica ice melt (DeConto & Pollard, 2016) (Figure 1).
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Figure 1. Possible future sea levels for different greenhouse gas emission pathways.
Figure 1 is entitled ‘Possible future sea levels for different greenhouse gas emission pathways’. There are 6 lines on the graph, each a solid colour for ‘low’, ‘intermediate-low’, ‘intermediate’, ‘intermediate-high’, ‘high’ and ‘extreme’. The vertical axis is labelled ‘Change in sea level (meters)’, beginning at -0.5 to 2.5, in increments of 0.5 meters. At 0 meters, there is a straight dotted line marker spanning the graph labelled ‘2000 sea level’. The horizontal axis is labelled ‘year’, beginning in 1800 to 2100, in increments of 50 years. In the graph, all 6 lines start at -0.1 meters in 1800. The lines remain level until 1918, where ‘tide-gauge observations’ are annotated, all lines start to increase, reaching 0 meters by the year 2000, where ‘satellite observations’ are annotated. After 2000, the 6 lines diverge. The ‘low’ line rises to end at 0.3 meters in 2100. The ‘intermediate-low’ line rises to end at 0.5 meters in 2100. The ‘intermediate’ line rises to end at 1.0 meters in 2100. The ‘intermediate-high’ line rises to end at 1.5 meters in 2100. The ‘high’ line rises to end at 2.0 meters in 2100. The ‘extreme’ line rises to end at 2.5 meters in 2100. All data is approximate.
End Image Text Version
This text and image are from “Coastal Adaptation to Climate Change and Sea-Level Rise” by Garry Griggs and Borja G. Reguero, which is licensed under CC BY 4.0 , with minor edits made by Trish Corbett.
Sustainable coastal infrastructure to combat sea-levels rising
Throughout the millions of years that these coastal ecosystems have existed, they have been able to keep pace with sea level fluctuations of more than 100 m, as evidenced by the very existence of these habitats or ecosystems today. However, added pressures on these ecosystems currently threatens their potential to keep pace with sea-level rise and affects their resilience to storm impacts (Lovelock et al., 2015; Perry et al. 2018; Rodriguez et al., 2014; Sasmito et al., 2015), therefore threatening their future effectiveness for flood and erosion reduction.
In order to adapt to the rising conditions, sustainable infrastructure that can withstand future conditions and potentially reduce the impacts on coastal communities are needed.
This text is from “Coastal Adaptation to Climate Change and Sea-Level Rise” by Garry Griggs and Borja G. Reguero, which is licensed under CC BY 4.0 , with minor edits made by Trish Corbett.
Open the sections below to explore some strategies to combatting sea-level rising.
Soft Protection Approaches and Working with Natural Processes Rather Than against Them
Soft Protection Approaches and Working with Natural Processes Rather Than against Them
The rising costs of coastal armouring and its intrinsic challenges in a changing climate has driven an increasing interest in other soft approaches. These approaches include a growing number of ‘engineering’ and ’building with nature’ initiatives that leverage natural ecosystems for their coastal protection value (Bridges, 2018; Judge et al., 2017; NOAA, 2015; Sutton-Grier, Wowk., & Bamford, 2015). Examples of “soft” approaches are increasing and include managed sediment relocation and beach and dune restoration with plants and landscape reshaping, as well as other living shorelines alternatives (e.g., oyster reefs).
This text is from “Coastal Adaptation to Climate Change and Sea-Level Rise” by Garry Griggs and Borja G. Reguero, which is licensed under CC BY 4.0 , with minor edits made by Trish Corbett.
Armouring or hardening the shoreline
Armouring or hardening the shoreline
Whether rock revetments, seawalls, levees or floodwalls, or any of a variety of other engineered or non-engineered structures, hardening or armouring the shoreline has been the most common historical approach to coastal erosion, shoreline retreat or flooding. These solutions aim to protect the shore by defending against elevated water levels or wave impacts. There is a long global history of coastal armouring, but in most cases, these structures were not built with their potential impacts to the surrounding environment and shoreline in mind. The potential effects of hardening the shoreline include visual impacts; loss of public beach due to placement of the structure on the beach; loss of the sand previously provided by the eroding cliff, bluff or dune being armoured; passive erosion or the gradual loss of the beach fronting the armour with a continuing rise in sea level (Griggs & Patsch, 2019).
“Sea wall at La Crabiere” by Oliver Dixon is licensed under CC BY-SA 2.0
It is important to understand that coastal armouring (including seawalls and revetments) protects what is behind the armour, at the cost of the fronting beach. Combating erosion with a hard structure parallel to the shoreline is a choice to not protect the beach at that location. It is only a matter of time before beaches in front of hard armouring structures will be flooded or disappear with a rising ocean (Griggs & Patsch, 2019). Structures also produce shoreline encroachment and coastal habitat squeeze (Leo et al., 2019). Coastal development and coastal armouring present physical barriers for the natural inland migration of coastal habitats, and changes in hydrological connectivity reduce sediment inputs and the potential for vertical accretion.
This text is from “Coastal Adaptation to Climate Change and Sea-Level Rise” by Garry Griggs and Borja G. Reguero, which is licensed under CC BY 4.0 , with minor edits made by Trish Corbett.
Natural or ‘green’ infrastructure
Natural or ‘green’ infrastructure
Along many coastlines where coastal ecosystems provide protection, one important strategy is maintaining and enhancing this “natural infrastructure”. The term “natural infrastructure” recognises the value that ecosystems, such as coral reefs, mangroves, salt marshes, beach and dune systems and vegetation (emerged or submerged), offer by attenuating waves, reducing the impacts of sea-level rise and retaining sediment or building land (Temmerman et al., 2013; Temmerman et al., 2015). For example, reefs (Chowdhury et al., 2019; Harris et al. 2021; Quataert et al., 2015; Reguero et al., 2021; Scyphers et al., 2011), seagrasses (Ondiviela et al., 2014) or saltmarshes and beach and dune systems can be effective in protecting against the impact of storms (Gracia et al., 2018; Hanley et al., 2014; Narayan et al., 2016) under certain conditions. Such protection can be very valuable. For many of these coastlines, including tropical nations and small island states at the forefront of the impacts of climate change, maintaining this natural infrastructure may be one of the most cost-effective adaptation strategies, at least over the short term.
This text is from “Coastal Adaptation to Climate Change and Sea-Level Rise” by Garry Griggs and Borja G. Reguero, which is licensed under CC BY 4.0 , with minor edits made by Trish Corbett.
Green or Gray approach?
Green or Gray approach?
The figure below shows the range of green or softer techniques through to gray or harder techniques such as coastal armouring.
This text, images and their associated captions are from “Coastal Adaptation to Climate Change and Sea-Level Rise” © 2021 by Garry Griggs and Borja G. Reguero, which is licensed under CC BY 4.0.
Figure 2 Image Text Version
Figure 2. Range in coastal protection approaches from green to gray with those on the left (“living or partially living”) suitable only for low wave energy environments.
Figure 2 is entitled ‘Range in coastal protection approaches from green to gray with those on the left (“living or partially living”) suitable only for low wave energy environments’. This diagram shows a scale from ‘green-softer techniques’ which impacts living shorelines to ‘gray-harder techniques’ which impacts coastal structures. From green to gray and left to right, each of the 6 techniques are detailed below.
Vegetation only (green)
Provides a buffer to upland areas and breaks small waves. Suitable for low wave energy environments.
Edging (green)
Added structure holds the toe of existing or vegetated slope in place. Suitable for most areas except high wave energy environments.
Sills (green)
Parallel to vegetated shoreline, reduces wave energy, and prevents erosion. Suitable for most areas except high wave energy environments.
Breakwater (gray)
(vegetation optional) – Offshore structures intended to break waves, reducing the force of wave action, and encourage sediment accretion. Suitable for most areas.
Revetment (gray)
Lays over the slope of the shoreline and protects it from erosion and waves. Suitable for sites with existing hardened shoreline structures.
Bulkhead (gray)
Vertical wall parallel to the shoreline intended to hold soil in place. Suitable for high energy settings and sites with existing hard shoreline structures.
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Activity: Innovative infrastructure project examples
Watch the videos below to learn about some innovative infrastructure project examples.
Activity: Test your Knowledge
Test your knowledge in the quiz below:
Activity Text Version
Activity: Test your Knowledge
This exercise invites readers to answer questions to test their knowledge, based on the sustainable coastal infrastructure information above. Questions and answers are listed below.
Question 1
A new breakwater is replacing the old Warrnambool breakwater. The decision has been made it will go ahead with no consideration of it’s removal or position. Which of the following options would be the best option to support the environment, society and the economy?
- Utilise innovative bio-cement structures that create habitat for different organisms and substrate for colonisation on the Lady Bay side of the breakwater.
- Create a replica of the current breakwater as is and restrict people accessing it or fishing from it.
- Create a replica of the current breakwater as is
- Utilise innovative bio-cement structures that create habitat for different organisms and substrate for colonisation on either side of the breakwater.
Answers to question 1
Utilise innovative bio-cement structures that create habitat for different organisms and substrate for colonisation on either side of the breakwater.
Question 2
True or False. Coastal armouring such as seawalls aims to defend coastlines against coastal erosion and water level rise, but is a decision not to protect the beach at that location as the ocean will eventually reach the structure.
Answers to question 2
True
Question 3
Select the correct statement. Natural or ‘green’ infrastructure:
- Utilises natural habitats, such as mangroves, to reduce the impacts of sea-level rise
- Has be be used in combination with anthropogenic coastal structures to be successful in protecting coastal communities
- Does not provide viable protection from sea-level rise
- Utilises natural materials, such as timber, to build coastal structures
Answers to question 3
- Utilises natural habitats, such as mangroves, to reduce the impacts of sea-level rise
End Activity Text Version
References
Bridges, T. S., Bourne, E. M., King, J. K., Kuzmitski, H. K., Moynihan, E. B., & Suedel, B. C. (2018). Engineering with nature: An atlas (No. ERDCELSR188). https://apps.dtic.mil/sti/html/tr/AD1081504/
Chowdhury, M. S. N., Walles, B., Sharifuzzaman, S. M., Shahadat Hossain, M., Ysebaert, T., & Smaal, A. C. (2019). Oyster breakwater reefs promote adjacent mudflat stability and salt marsh growth in a monsoon dominated subtropical coast. Scientific reports, 9(1), 8549. https://doi.org/10.1038/s41598-019-44925-6
DeConto, R. M., & Pollard, D. (2016). Contribution of Antarctica to past and future sea-level rise. Nature, 531(7596), 591-597. https://doi.org/10.1038/nature17145
Gracia, A., Rangel-Buitrago, N., Oakley, J. A., & Williams, A. T. (2018). Use of ecosystems in coastal erosion management. Ocean & coastal management, 156, 277-289. https://doi.org/10.1016/j.ocecoaman.2017.07.009
Griggs, G. B. (2005). The impacts of coastal armoring. Shore and beach, 73(1), 13-22.
Hanley, M. E., Hoggart, S. P. G., Simmonds, D. J., Bichot, A., Colangelo, M. A., Bozzeda, F., … & Thompson, R. C. (2014). Shifting sands? Coastal protection by sand banks, beaches and dunes. Coastal Engineering, 87, 136-146. https://doi.org/10.1016/j.coastaleng.2013.10.020
Harris, D. L., Rovere, A., Casella, E., Power, H., Canavesio, R., Collin, A., … & Parravicini, V. (2018). Coral reef structural complexity provides important coastal protection from waves under rising sea levels. Science advances, 4(2), eaao4350. https://doi.org/10.1126/sciadv.aao4350
Judge, J., Newkirk, S., Leo, K., Heady, W., Hayden, M., Veloz, S., & Small, M. (2017). Case Studies Of Natural Shoreline Infrastructure In Coastal California.
Leo, K. L., Gillies, C. L., Fitzsimons, J. A., Hale, L. Z., & Beck, M. W. (2019). Coastal habitat squeeze: A review of adaptation solutions for saltmarsh, mangrove and beach habitats. Ocean & Coastal Management, 175, 180-190. https://doi.org/10.1016/j.ocecoaman.2019.03.019
Lovelock, C. E., Cahoon, D. R., Friess, D. A., Guntenspergen, G. R., Krauss, K. W., Reef, R., & Triet, T. (2015). The vulnerability of Indo-Pacific mangrove forests to sea-level rise. Nature, 526(7574), 559-563. https://doi.org/10.1038/nature15538
Narayan, S., Beck, M. W., Reguero, B. G., Losada, I. J., Van Wesenbeeck, B., Pontee, N., & Burks-Copes, K. A. (2016). The effectiveness, costs and coastal protection benefits of natural and nature-based defences. PloS one, 11(5), e0154735. https://doi.org/10.1371/journal.pone.0154735
NOAA. (2015). Guidance for Considering the Use of Living Shorelines. pp. 1–36. Available online: https://repository.library.noaa.gov/view/noaa/71191
Ondiviela, B., Losada, I. J., Lara, J. L., Maza, M., Galván, C., Bouma, T. J., & van Belzen, J. (2014). The role of seagrasses in coastal protection in a changing climate. Coastal Engineering, 87, 158-168. https://doi.org/10.1016/j.coastaleng.2013.11.005
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Quataert, E., Storlazzi, C., Van Rooijen, A., Cheriton, O., & Van Dongeren, A. (2015). The influence of coral reefs and climate change on wave‐driven flooding of tropical coastlines. Geophysical Research Letters, 42(15), 6407-6415. https://doi.org/10.1002/2015GL064861
Reguero, B. G., Storlazzi, C. D., Gibbs, A. E., Shope, J. B., Cole, A. D., Cumming, K. A., & Beck, M. W. (2021). The value of US coral reefs for flood risk reduction. Nature Sustainability, 4(8), 688-698. https://doi.org/10.1038/s41893-021-00706-6
Rodriguez, A. B., Fodrie, F. J., Ridge, J. T., Lindquist, N. L., Theuerkauf, E. J., Coleman, S. E., & Kenworthy, M. D. (2014). Oyster reefs can outpace sea-level rise. Nature climate change, 4(6), 493-497. https://doi.org/10.1038/nclimate2216
Sasmito, S. D., Murdiyarso, D., Friess, D. A., & Kurnianto, S. (2016). Can mangroves keep pace with contemporary sea level rise? A global data review. Wetlands Ecology and Management, 24(2), 263-278. https://doi.org/10.1007/s11273-015-9466-7
Scyphers, S. B., Powers, S. P., Heck Jr, K. L., & Byron, D. (2011). Oyster reefs as natural breakwaters mitigate shoreline loss and facilitate fisheries. PloS one, 6(8), e22396. https://doi.org/10.1371/journal.pone.0022396
Sutton-Grier, A. E., Wowk, K., & Bamford, H. (2015). Future of our coasts: The potential for natural and hybrid infrastructure to enhance the resilience of our coastal communities, economies and ecosystems. Environmental science & policy, 51, 137-148. https://doi.org/10.1016/j.envsci.2015.04.006
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